Stress Analysis of Crane Hook and Validation by Photo-Elasticity

Crane Hooks are highly liable components and are always subjected to failure due to accumulation of large amount of stresses which can eventually lead to its failure. To study the stress pattern of crane hook in its loaded condition, a solid model of crane hook is prepared with the help of CMM and CAD software. Real time pattern of stress concentration in 3D model of crane hook is obtained. The stress distribution pattern is verified for its correctness on an acrylic model of crane hook using Diffused light Polariscope set up. By predicting the stress concentration area, the shape of the crane is modified to increase its working life and reduce the failure rates.

Small-Force Measurement by Photo-Elastic Transducer

The use of stress-induced changes in a crystal of a monolithic solid-state laser by external force as a way for micro-force detection and measurement is described. In fact, the application of an unknown force on the resonator-amplifier crystal of a solid-state laser leads to a measurable change in the frequency of the beat note associated with the orthogonal polarisation components of the oscillating laser mode. Here we report our first measurements of the sensitivity of a photo-elastic force sensor, realised with a monolithic (4 × 4) mm plano-convex cylindrical crystal, and compare them with the results obtained by other authors for different configurations and dimensions of the laser sensor. The reported results are in a good mutual agreement but show notable discrepancies with theoretical predictions, especially for high sensitivities obtained when the dimensions of the laser sensor are small.

Interfacial stress transfer behavior in a specially-shaped fiber/matrix pullout test

Specially designed fibers are widely used in engineering practice because the specially-designed shape can help to improve the bonding strength of the fiber and the interface. Studied in this paper is the interfacial shear stress transfer behavior on both sides of the specially designed fiber when it is being pulled out; in which automatic analysis of three-dimensional photoelasticity is employed and the finite element method is adopted. The results show that the stress transfer occurs mainly in the region near the fiber＇s embedded end where the stress reaches its critical point, leading to debonding of the interface. Before debonding, as the pullout loading increases, the peak value of shear stress transfers along the fiber from the embedded end to the interior of the matrix, and then stops at the hooked part of the fiber because of its impediment. When the interface begins to debond as the load increases, the shear stress can be transferred to the hooked part.

Contact Stress Distribution of a Pear Cam Profile with Roller Follower Mechanism

The problem of this paper is the high contact stress at the point of contact between the cam and the follower.A pear cam and roller follower mechanism were studied and analyzed for different position of the follower and different contact compression load.The objective of this paper is to study the effect of contact compression load on the contact stress distribution of the cam profile at the point of contact.Four different positions of the follower with the cam was considered(0°,90°,180°,and 270°).The theory of circular plate was applied to derive the analytic solution of the contact stress.The numerical simulation had been done using ANSYS Ver.19.2 package to determine the contact stress,while SolidWorks software was used to investigate follower displacement,velocity,and acceleration.Four distinct values of the compression contact load,such as 3.121 N,6.242 N,9.364 N,and 12.485 N,were used in the numerical simulation.In the experiment setup,a photo-elastic technique was carried out in the field of polarized light to exhibit the stress distribution on the cam specimen.The annealed PSM-4 backalate material was used in the experiment setup.The experimental value of contact stress was checked and verified analytically and numerically at the point of contact.The innovation in this paper the use of spring-damper system which reduce the value of contact stress at the point of contact.The contact stress was maximum 2.136 MPa when the follower located at 270°with the cam,while the contact stress was minimum 1.802 MPa when the follower located at 180°at compression load 12.485 N.

Structural formation and evolution mechanisms of fracture plugging zone

A coupled CFD-DEM method is used to simulate the formation process of fracture plugging zone.A photo-elastic system characterizing mesoscale force chain network developed by our own is used to model the pressure evolution in fracture plugging zone to reveal the evolution mechanism of the structure of fracture plugging zone.A theoretical basis is provided for improving the lost circulation control effect in fractured reservoirs and novel methods are proposed for selecting loss control materials and designing loss control formula.CFD-DEM simulation results show that bridging probability is the key factor determining the formation of fracture plugging zone and fracture plugging efficiency.Critical and absolute bridging concentrations are proposed as the key indexes for loss control formula design.With the increase of absolute bridging concentration,the governing factor of bridging is changed from material grain size to the combination of material grain size and friction force.Results of photo-elastic experiments show that mesoscale force chain network is the intrinsic factor affecting the evolution of pressure exerting on the fracture plugging zone and determines the macroscopic strength of fracture plugging zone.Performance parameters of loss control material affect the force chain network structure and the ratio of stronger force chain,and further impact the stability and strength of fracture plugging zone.Based on the study results,the loss control formula is optimized and new-type loss control material is designed.Laboratory experiments results show that the fracture plugging efficiency and strength is effectively improved.

Experimental investigation on the cracking behavior of 3D printed kinked fissure

Uniaxial compression tests were carried out for 3 D printed samples having various types of kinked fissures by using the rock mechanics servo-controlled testing system. Photo-elastic technique is adopted to characterize and visualize the stress distribution and evolution of 3 D printed models subjected to vertical compression. The stress field in the loading process can clearly be captured via a high-speed camera. The results showed that fringes around the kinked fissure tips formed a central symmetrical interference fringe pattern, and failure firstly occurred at interference fringe of highest order. Two failure types i.e. tip-cracking and non-tip-cracking are categorized on the basis of crack propagation pattern of 3 D printed samples. Tensile crack propagation of wing cracks is the main form of failure of the antisymmetric kinked fissures, but the inclination of the branch fissures also played a key role on the location of initial fracture. The finite element method was applied to numerically simulate the process of crack propagation. The isochromatic fringe patterns are in good agreement with the experimental investigation. The current work gives an insight for implication of advanced technique to quantify and visualize the distribution of stress field, and provides further understanding of kinked fissure behavior at failure.